Is it effective to have a furnace in crawl space?

Furnaces are typically installed in the homeowners’ closets, attics, cellars, garages, or utility rooms. A crawl space furnace is an effective method for heating a home. During the colder months, the furnace is responsible for providing warmth by warming the air that is then circulated throughout the building.

Always make sure to check the International Residential Code for requirements concerning crawl space safety.

furnace in crawl space

What kind of furnace can be placed in a crawlspace?

Because of limited space, some furnaces are crawl space-only. A furnace must meet home regulations and standards to ensure a safe environment, according to new information.

A professional inspector can help you choose a crawl space size. 

Crawlspace furnaces usually circulate horizontally. The angled bed circulates air from one side to the other. Vertical furnaces are ideal for crawlspaces due to their size.

Gas furnaces 

Unknowingly, a gas furnace can catch fire. Oil or gas furnace needs fresh air. Encapsulating a crawl space requires adding airflow or natural ventilation, which costs money. If local codes and regulations are followed, oil and gas furnaces can be installed in the crawl space.

Is it effective to have a furnace in crawl space?

The benefits of installing a furnace in a crawl space

A furnace can be installed in the basement, utility room, or garage, depending on the house’s layout and size. Consider these factors before installing a furnace in your crawl space. 

Saving energy is one benefit. By installing a furnace in your crawl space, you can heat the house more efficiently by circulating warm air throughout. This can reduce heating costs. 

It can also improve home comfort. By heating the crawl space, you create an extra warm room in your home. On cold days, this can be a lifesaver. 

Consider the pros and cons before installing a furnace in your crawl space.

Important safety regulations for furnaces in a crawl space

There are safety regulations for furnaces in crawl areas. 

The furnace must be installed per IRC. For your safety, follow the manufacturer’s specific instructions when installing your furnace. 

It must be installed away from flammable and combustible materials. To avoid carbon monoxide buildup, the furnace must have natural ventilation from the outside (fresh air).

Base flood elevation: If your crawl space is lower than the base flood elevation, you need drains to prevent flooding.

Fire-protected space: Any crawl space must have fire-protected flooring installed immediately. The room should be easily accessible as well. It’s also important to remember that the crawl space is an enclosed space, and as such, can quickly become a dangerous place if there’s a fire. 

Make sure you have a working smoke alarm in the crawl space and consider installing an approved sprinkler system as well.

Is it effective to have a furnace in crawl space?

Combustion air openings for furnaces in a crawl space

If you’re installing a furnace in a crawl space, you’ll need to provide combustion air. This is the air that the furnace needs to burn properly, and it can come from either outdoors or inside the home.

The local codes require that you have at least one combustion air opening for every 750 square feet of crawl space. 

Clear space: The area immediately in front of the unit is the combustion air opening should be at least 6 inches clear space. You can meet this requirement by installing a duct from the crawl space to the outdoors with fresh air.

Or, if the crawl space is connected to the basement, you can use the basement as your combustion air opening.

Preventing dirty air from entering the home with proper encapsulation

Your furnace is likely pulling polluted air from the dirt floor in a crawl space. It is also cold and damp. 

Encase your crawlspace furnace. Encapsulation prevents dirty air from entering the home and regulates temperature. This reduces energy costs in the winter by preventing heat loss. 

Crawl space encapsulation should be breathable and water-resistant. A breathable vapor barrier prevents mold growth in climate-controlled areas and allows for even home heating. Choose a material that resists dirt, water, and other elements. 

Encapsulating your crawl space keeps humid air and ground moisture out.

Trap door opening requirements for furnaces in crawl spaces

IRC specifies crawl space furnace doorway size. The trap door must be 2′ high and 2′ wide. This makes the furnace easily accessible. If the trap door opening is any smaller, it can create a safety hazard and make furnace maintenance difficult. 

If you plan to install multiple furnaces in your crawl space, each doorway opening must be the same size. So, neither furnace needs to be serviced through a small or large opening.

Is it effective to have a furnace in crawl space?

Best practices for installing a furnace in a crawl space

Install a crawl space furnace properly. First, follow IRC for safety. State and local codes may add requirements. 

Insulated duct board reduces noise and improves efficiency. This product fits in crawl areas. Make sure the furnace is well-ventilated and away from flammable walls or cabinets. Reduce noise by insulating the crawl space and furnace installation site. Consider a state- or locally-approved energy-efficient model to save money.

Understanding the International Residential Code concerning furnace installation

When installing a furnace in a crawl space, follow the International Residential Code’s security requirements. The code ensures safe and stable furnaces to prevent accidents. 

The International Residential Code requires all furnaces in crawl areas to be securely attached to a rigid structure or wall and 18 inches above any combustible material, such as insulation or ventilation ducts.

It requires a pressure relief valve and secure access doors. 

By understanding these basic regulations, you can make sure your furnace is safe and secure for years of efficient heat.

Moldy crawlspace. It is summer. EPA says this is perfect for mold. The HVAC unit is a crawlspace air intake that picks up mold spores. Spreading spores. Microscopic spores escape standard filters.

The best solution: crawl space encapsulation

There is only one easy and fast solution to the crawl space problem. Encapsulated crawl space. In essence, it turns the crawl space into an isolated, insulated basement. How do crawlspaces work?

There’s nothing foul-smelling. Improved indoor environment. Fewer allergies. Efficiency in the air quality. Reduced electricity costs.

Is it effective to have a furnace in crawl space?

Should I air condition my crawl space?

Is the air conditioner helping in keeping you dry? It is advisable to have a conditioned (closing or sealed) crawlspace. The room would then be covered and sealed using an enclosure.

After that, it’s necessary to install the correct insulation and finally a heating and cooling system which can pump the cool air from the basement to the crawl area.

Crawl space furnace dimensions

A general rule of thumb is to leave at least 30 inches of space between the walls and the sides of a vertical furnace. When you hire a professional HVAC contractor near you, the space will be designed in accordance with your local area’s codes and will maximize the performance and efficiency of your furnace.

Do I need a dehumidifier in my conditioned crawl area?

The use of dehumidifiers helps prevent mold growth on floor joists in crawl rooms. Alternatively, dehumidification may be useless for a capsulated space.

Proper insulation in crawl rooms keeps these areas dry and neat.

The spaces can be dried through a supply of air by allowing air-conditioned ventilation to enter crawl rooms in the building.

Installation of horizontal furnaces in a crawlspace

Horizontal flow furnaces are typically installed in very small spaces that cannot easily be moved by traditional units. Typically, these horizontal flow furnaces have lower energy consumption but do not require much space in an area.

Is it effective to have a furnace in crawl space?


If your crawl space contains a furnace, be sure to leave a vent open so that stale air can escape. In addition to that, you require an air trap entrance. If the contaminated air is unable to leave the building, the furnace will become filthy and will require more frequent cleaning. Without a trapdoor, the furnace will not function properly.


How much does it cost to get your furnace installed? 

Installing a crawl space furnace can cost $2,000 to $15,000 or more. Cost includes furnace, equipment, materials, and labor. Most homes with this setup cost $5,500.

Is it OK to have furnace in crawl space?

If you use an adequate furnace, it is perfectly okay! Vertically flowing furnaces are particularly important in crawl areas. They are designed to be horizontally positioned, and they circulate air on both sides.

Is HVAC better in attic or crawl space?

More efficient ducts: The attic’s heating systems are close enough to provide heat for multiple levels of a residence. The system won’t require extensive and long ducts and ductwork to distribute heat to all rooms when compared with furnaces and HVACs in crawl spaces and basements.

Can HVAC go in crawl space?

HVAC systems work well in crawl spaces.

Is heating a crawl space a good idea?

Multiple factors make crawl space heating and insulation a cost-saver. The ducts and pipes that distribute heated air and water in your home pass through the crawl area.

Read Also About Fixing Up Crawl Spaces

Robert Brooks

I have an engineering background. I have my own house, where I live with my wife and children. I want to say that the most important thing when equipping a house is to choose the right heating, ventilation, and air conditioning systems.

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